misc/cgo/testcarchive: skip flaky SIGPROF test on darwin

Updates #19320.

Change-Id: Id38df033e3f0873986e668c8ff3855b6e08407a9
Reviewed-on: https://go-review.googlesource.com/69114
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/cgo/testcarchive/carchive_test.go

@@ -549,6 +549,8 @@ func TestSIGPROF(t *testing.T) {
 	switch GOOS {
 	case "windows", "plan9":
 		t.Skipf("skipping SIGPROF test on %s", GOOS)
+	case "darwin":
+		t.Skipf("skipping SIGPROF test on %s; see https://golang.org/issue/19320", GOOS)
 	}
 
 	t.Parallel()